TPA treatment of macrophages (M0) results in prostaglandin (PG)E2 production and a soluble factor(s) promoting tumor cell growth. Interferon (IF) and IF inducers enhance M0 and Natural Killer (NK) cell tumoricidal activity which is negated by PG. The ability of tumors to produce PGE may contribute to their ability to escape immune surveillance. Glucocorticoid hormones, PG, and cAMP inhibit IF induced M0 tumoricidal activity. Maleic divinyl ether (MVE) of various molecular weights enhance M0 and NK cell tumoricidal activity. A synergistic anti-tumor therapeutic effect is achieved by combining MVE with cytoreductive therapy. Human chorionic gonadotropin (HCG) expresses a dual effect: it enhances M0 and NK cell tumor lytic activity and PG formation which, in turn, limits T cell effects. High titers of IF induced by Poly ICLC correlate with the enhanced M0 and NK cell tumor lytic effect. Azimexon treatment resulted in increased granulocyte-M0 colony forming cells in spleen & bone marrow. Highly effective therapeutic response was achieved against an alveolar Ca with combined cytoreductive chemotherapy and MVE. MVEs' effective adjuvanticity to tumor cell vaccines appear to act through the augmentation of M0 antigen processing.